Pin exported surface to intended API and shrink

[jserv]

libX11-compat exported every non-static symbol (~1100), leaking ~400 internal helpers into the dynamic table. Restrict the exported set to the surface the project already enumerates, and shrink the library along the way.

Generate a linker export list (ELF version script / Mach-O -exported_symbols_list) from the union of {api,shim,private}-symbols.txt (the core->libXft private contract) and whitebox-symbols.txt, intersected with the symbols the build actually defines. The intersection keeps the list valid under strict linkers (lld and binutils 2.43 default to --no-undefined-version), so the manifests can stay a cross-platform superset. GLX/FORMAT identity is tracked by a single link-config stamp that regenerates the map and relinks on change.

Export the core-defined libX11 underscore ABI (_Xdebug, _XGetHostname, ...) by pattern: real libX11 exports those globals and legacy clients link them directly (violawww's libIMG references _Xdebug), which the X[A-Z]* manifests do not cover.

Shrink: -ffunction-sections/-fdata-sections plus --gc-sections / -dead_strip collect code no exported symbol reaches, notably the duplicated in-core Xft/Fc copy that only libXft-compat consumes. Install-time strip -x slims the deployed libraries a further ~6% while the dev build keeps local symbols for backtraces. A source pass marks 12 single-TU helpers static and deletes 2 dead functions.

Net exported surface: 727 (macOS) / 725 (Linux) = 682 public + 24 shim + 13 libXft-private + 7 underscore-ABI + 1 Motif-tier whitebox. Shipped library 588,720 to 524,192 bytes installed.

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Summary by cubic

Pin libX11-compat exports to the intended API and dead-strip unused code to shrink the installed library (588,720 → 524,192 bytes). Keeps legacy _X* ABI available while hiding ~400 internal helpers.

• Refactors

  • Generate export lists from tests/api-symbols.txt, tests/shim-symbols.txt, tests/private-symbols.txt, and tests/whitebox-symbols.txt, intersected with defined symbols; auto-regenerated on GLX/format changes; generator fails on missing/unreadable inputs.
  • Use ELF version script with --gc-sections on Linux and -exported_symbols_list with -dead_strip on macOS; keep _X* ABI exported by pattern; add tests/test-xlibint-link.c.
  • Add unpinned test twin libX11-compat-test.so for whitebox tests; shipped libX11-compat.so remains pinned.
  • Enable code GC with -ffunction-sections -fdata-sections; mark 12 helpers static and remove 2 dead functions.
  • Tighten libXft-compat link with -Wl,--no-undefined on Linux; gate off under -fsanitize builds.

• Migration

  • Installed libs are stripped of local symbols via strip -x; on macOS they are re-signed after strip. Override STRIP=: (or a custom tool) if needed.

^{Written for commit 7851587. Summary will update on new commits.}

[jserv]

Addressed in e9a1c5b.

Fixed:

• gen-export-list.sh (both P1s): the manifests are now read in a checked step, so a missing or unreadable manifest fails the build instead of being masked by the trailing sort. The || true is removed from the comm intersection so a defined-syms read error propagates; comm already returns 0 for an empty intersection, so the legitimate empty case still succeeds. Confirmed: a missing manifest or defined-syms now exits non-zero, an empty intersection exits 0.
• install.mk (P2): strip -x rewrites the Mach-O and invalidates the ad-hoc signature ld64 puts on arm64 binaries, so the install now re-signs with codesign --force --sign - after strip on Darwin (a no-op : elsewhere), rather than relying on the STRIP=: escape hatch. Verified the installed dylib passes codesign -v and dlopens.

Not defects, so left as-is:

• library.mk:86 (underscore ABI on macOS): the ABI is exported. nm prints the Mach-O double underscore __Xdebug; the Darwin sed 's/^_//' strips one to _Xdebug, which the ^_X match keeps; the macho formatter re-adds the underscore. Verified all 7 _X* globals (_Xdebug, _XGetHostname, _XDefaultError, _XIDHandler, _XInitImageFuncPtrs, _XrmInternalStringToQuark, _XSeqSyncFunction) are exported on macOS.
• library.mk:113 (.so vs .dylib twin): compat libraries in this tree use .so on both platforms (TARGET := $(OUT)/libX11-compat.so); .dylib is only autoconf-built Motif. The whitebox suite already runs on macOS and the .so-named Mach-O twin builds and loads there.

Validated on macOS and Linux (docker ubuntu 24.04, clang-18, GNU ld 2.42): check-unit, symbol-coverage, generator error-propagation, and make install producing a codesign-valid stripped dylib.